The food and pharmaceutical industries have developed an interest in higher polyol polyesters of fatty acids for use as low calorie fats in food products and as pharmaceutical agents, e.g., for the lowering of blood cholesterol levels. U.S. Pat. No. 3,600,186, Mattson and Volpenhein, issued Aug. 17, 1971, describes low calorie food compositions formed by replacing at least a portion of the fat content of food products with higher polyol fatty acid polyesters. U.S. Pat. No. 3,954,976, Mattson and Volpenhein, issued May 4, 1976, describes pharmaceutical compositions for inhibiting the absorption of cholesterol comprising effective unit dosage amounts of higher polyol fatty acid polyesters, as well as the method for treating hypercholesterolemia using these polyesters. Additional pharmaceutical uses are described in U.S. Pat. No. 4,241,054, Volpenhein and Jandacek, issued Dec. 23, 1980 (removal of halogenated toxins from the body), and U.S. Pat. No. 4,264,583, Jandacek, Apr. 28, 1981 (treatment of gallstones).
The polyol polyesters are also useful as emulsifiers.
Typical syntheses of polyol polyesters involve reaction of lower monohydric alcohol esters (e.g. methyl esters) of fatty acids with the polyol. See for example U.S. Pat. Nos. 3,963,699 Rizzi et al., issued June 15, 1976; 4,518,722, Volpenhein, issued May 21, 1985 and 4,517,360, Volpenhein, issued May 14, 1985, all incorporated by reference herein.
The fatty lower alkyl esters used in the preparation of the polyol polyesters are typically derived from natural fats and oils such as soya oil, cottonseed oil, sunflower oil, etc. Such esters contain substantial quantities of conjugated and conjugatable cis and trans unsaturated fatty acid chains. When such fatty esters have been subjected to atmospheric oxidation (as indicated by measurement of their peroxide value), they have an even higher propensity to conjugate. When these esters are reacted with polyols in the presence of a basic catalyst (e.g., potassium carbonate) to produce the corresponding polyol polyesters, the resulting product is usually found to have a brownish-yellow color. Such color is undesirable, especially for situations where the polyol polyesters is to be used in foods or other consumer products.
An object of the present invention is to provide lower alkyl esters of fatty acids which, when converted to polyol polyesters by base-catalyzed transesterification with polyols, produce polyol polyesters having low color content.
Another objective of the present invention is to provide fatty polyol polyesters having reduced color content.
Another objective is to provide a process for preparing fatty polyol polyesters having reduced color content.